package com.alvinlkk.basic.chapter21;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

class Pair  {
    private int x;
    private int y;
    
    public Pair(int x, int y) {
        this.x = x;
        this.y = y;
    }
    
    public Pair() {
        this(0, 0);
    }
    
    public int getX() {return x;};
    
    public int getY() {return y;};
    
    public void incrementX() { x ++; }
    
    public void incrementY() { y ++;}
    
    public String toString() {
        return "x:" + x + ", y:" + y;
    };
    
    public class PairValuesNotEqualException extends RuntimeException {
        
        public PairValuesNotEqualException() {
            super("Pair values not equal:" + Pair.this);
        }
    }
    
    public void checkState() {
        if(x != y) {
            throw new PairValuesNotEqualException();
        }
    }
    
}

abstract class PairManager {
    AtomicInteger checkCount = new AtomicInteger(0);
    protected Pair p = new Pair();
    private List<Pair> storage = Collections.synchronizedList(new ArrayList<Pair>());
    
    public synchronized Pair getPair() {
        return new Pair(p.getX(), p.getY());
    }
    
    public void store(Pair p) {
        storage.add(p);
        
        try {
            TimeUnit.MILLISECONDS.sleep(50);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    
    public abstract void increment();
}

class PairManager1 extends PairManager {

    @Override
    public synchronized void increment() {
        p.incrementX();
        p.incrementY();
        store(getPair());
    }
    
}

class PairManager2 extends PairManager {

    @Override
    public void increment() {
        Pair temp;
        synchronized (this) {
            p.incrementX();
            p.incrementY();
            temp = getPair();
        }
        store(temp);
    }
}

class PairManipulator implements Runnable {
    
    private PairManager pm;
    
    public PairManipulator(PairManager pm) {
        this.pm = pm;
    }
    
    @Override
    public void run() {
        while (true) {
            pm.increment();
        }
    }
    
    @Override
    public String toString() {
        return "Pair: " + pm.getPair() + "checkCounter = " + pm.checkCount.get();
    }
    
}

class PairChecker implements Runnable {
    
    private PairManager pm;
    
    public PairChecker(PairManager pm) {
        this.pm = pm;
    }
    
    @Override
    public void run() {
        while (true) {
            pm.checkCount.incrementAndGet();
            pm.getPair().checkState();
        }
    }
    
}

public class CriticalSection {
    static void testApproaches(PairManager pman1, PairManager pman2) {
        ExecutorService exec = Executors.newCachedThreadPool();
        PairManipulator
            pm1 = new PairManipulator(pman1),
            pm2 = new PairManipulator(pman2);
        PairChecker
            pc1 = new PairChecker(pman1),
            pc2 = new PairChecker(pman2);
        exec.execute(pm1);
        exec.execute(pm2);
        exec.execute(pc1);
        exec.execute(pc2);
        
        try {
            TimeUnit.SECONDS.sleep(5);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        
        System.out.println("pm1: " + pm1 + ", pm2: " + pm2);
        System.exit(0);
    }
    
    static void testSingle(PairManager pman1) {
        ExecutorService exec = Executors.newCachedThreadPool();
        PairManipulator
            pm1 = new PairManipulator(pman1);
        PairChecker
            pc1 = new PairChecker(pman1);
        exec.execute(pm1);
        exec.execute(pc1);
        
        try {
            TimeUnit.SECONDS.sleep(5);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        
        System.out.println("pm1: " + pm1);
        System.exit(0);
    }
    
    public static void main(String[] args) {
        PairManager pman1 = new PairManager1();
        PairManager pman2 = new PairManager2();
        testApproaches(pman1, pman2);
    }
}
